Simulation Gives Glimpse into Supernova's Chaotic Guts

Three-dimensional turbulent mixing in a stratified burning oxygen shell. The yellow ashes of sulfur are being dredged up from the underlying orange core.

Arnett, Meakin and Viallet/AIP Advances

Gallery

TheSupercomputerSupernova

View Caption+#1: Supernova Plasma Energy

Computer visualization is an essential tool for scientists to gain an insight to how complex physical, biological and chemical phenomena work. From protein structures to the detonation of supernovae, scientists are finding faster, more precise and more powerful means of simulating these systems using supercomputers.
One such supercomputer is the Blue Gene®/P housed at the U.S. Department of Energy's Argonne National Laboratory in Chicago where 160,000 computing cores work in parallel to process 557 trillion calculations per second. If you to tried to simulate an equivalent system on your standard home computer, it would take three years just to download the data! Turning that data into a usable model would be an impossible task.
Now, using a new technique called software-based parallel volume rendering, scientists at Argonne are able to visualize 3D models of supernovae.
In the visualization above, the various plasma energies of the expanding supernova are color coded, allowing the scientists to peer deep into the inner workings of the explosion, providing an invaluable look at this powerful astrophysical event.

Argonne National Laboratory

View Caption+#2: Moment of Detonation

In this visualization, the moment of detonation of a Type 1a supernova is modeled. This situation arises when a white dwarf star has accreted mass from a binary partner to a point when gravitational forces overcome the outward electron degeneracy pressure. The star collapses and it is thought that carbon fusion is initiated in the core, creating a supernova. The star is completely destroyed.
Around 1-2 × 1044 Joules of energy is released from Type 1a supernovae, ejecting matter and shock waves traveling at velocities of 3-12,000 miles per second (approximately 2-7% the speed of light).

Argonne National Laboratory

View Caption+#3: White Dwarf No More

The Type 1a supernova proceeds in the simulation, ripping through the white dwarf star.

Argonne National Laboratory

View Caption+#4: Complex Fluid Mechanics

Detailed visualizations of the nuclear combustion inside a supernova. The calculations are based on fluid mechanics, showing how the explosion rips through the star.

Argonne National Laboratory

View Caption+#5: Tycho's Nova

Advanced computational methods as being developed at Argonne National Laboratory will help astrophysicists understand how supernovae behave.
This is an image of the famous Tycho's Nova (known as SN 1572), the beautiful remnant of a Type 1a supernova.

NASA

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Supernovae are the deaths of massive stars that give birth to heavy elements, more stars, planets and, ultimately, life. These most violent explosions are the foundation for all the stuff we see in the Universe, but for such a fundamental phenomenon we know very little about how and why they ‘blow.’

In a new study by an international team of astrophysicists, a sophisticated computer simulation has been created in an effort to understand the 3-dimensional complexities inside a supernova. As expected, the dynamics in the guts of a collapsing star are complex, but this new model gives scientists the best ever look at how matter mixes when the supernova detonates, potentially explaining observations of supernovae that haven’t quite fitted our understanding of how we thought these gargantuan explosions worked.

In 1987, a supernova (1987A) detonated in the Large Magellanic Cloud, a nearby dwarf galaxy only 168,000 light-years away. This event caused some confusion in the astronomical community — like many cosmic phenomena, the observation didn’t quite match with our theoretical expectations. When studying the expanding cloud of supernova debris, astronomers noticed that material freshly ejected from the explosion was mixing with material the progenitor star had ejected some time before. This mixing was unexpected, suggesting that theoretical models needed refining.

Existing models assume a concentric, ‘shell-like’ structure of differentiated elements inside a star that is about to go supernova. As the massive star collapses under gravitational contraction (after exhausting its fusion fuel in the core), copious amounts of neutrinos are generated, rapidly leaching energy from the star’s interior. This has the effect of speeding up the contraction, accelerating the heating.

“It heats up and burns faster, making more neutrinos and speeding up the process until you have a runaway situation,” said W. David Arnett, of Astrophysics at the University of Arizona.

In an effort to understand this process, astrophysicists have turned to supercomputers for help. Often, because of technological restrictions, researchers will create a 1-D or 2-D model and make assumptions on the other dimensions. While this is effective, it often leads to a smooth transition between the layers inside the supernova. But this only tells half the story.

Snapshot of the simulation showing oxygen burning in a moderately stratified shell during a supernova.

Arnett, Meakin and Viallet/AIP Advances

Arnett is working with Casey Meakin and Nathan Smith, also at at the University of Arizona, and Maxime Viallet of the Max-Planck Institut fur Astrophysik, Germany, to develop a fully 3-dimensional model of a supernova. Their work now provides us with an even more violent and chaotic view of how a supernova detonates.

“We still have the concentric circles, with the heaviest elements in the middle and the lightest elements on top, but it is if someone put a paddle in there and mixed it around,” said Arnett. “As we approach the explosion, we get flows that mix the materials together, causing the star to flop around and spit out material until we get an explosion.

“That’s what see in supernova remnants, we see those ejections of star material, and how they mix with material expelled from the star during its final explosion. Other models cannot explain this,” he said.

With the help of supernova surveys, such as the Katzman Automatic Imaging Telescope (KAIT) and Palomar Supernova Factory, observations of stars as they become unstable and explode as supernovae are becoming more detailed, providing an unprecedented look into the death of stars. Interestingly, it’s not all about the massive explosion, the run-up to a supernova features many stellar complexities.

“Instead of going gently into that dark night, (the star) is fighting. It is sputtering and spitting off material. This can take a year or two. There are small precursor events, several peaks, and then the big explosion,” added Arnett. “Perhaps we need is a more sophisticated notion of what an explosion is to explain what we are seeing.”